Hot runner manifold system

ABSTRACT

A manifold system ( 50 ) comprising a main manifold ( 56 ) with a plurality of arms ( 64 ), a plurality of sub-manifolds ( 52 ) spaced from the main manifold ( 56 ) and communicating with the main manifold ( 56 ) through a plurality of melt transfer bushings ( 68 ) disposed between the main manifold ( 56 ) and the sub-manifolds ( 52 ). The melt transfer bushings ( 68 ) may include static mixers ( 140 ) to homogenize the melt. An air plate ( 70 ) is disposed between a backing plate ( 58 ) preferably housing the main manifold ( 56 ) and a manifold plate ( 54 ) preferably housing the sub-manifolds ( 52 ). The air plate ( 70 ) has a plurality of air channels ( 74 ) that communicate with valve gate nozzle actuators ( 90 ), which are received in actuator cavities ( 72 ) in the air plate ( 70 ). The air plate ( 70 ) is bolted to the manifold plate ( 54 ), and the backing plate ( 58 ) is bolted to the air plate ( 70 ) with bolting patterns not constrained by location of the main manifold ( 56 ) or sub-manifolds ( 52 ). The manifold system ( 50 ), as shown in FIG.  5,  has better thermal and geometric balance, closer nozzle spacing, and better bolting for less plate bowing.

TECHNICAL FIELD

The present invention relates, generally, to injection moldingequipment. More particularly, the invention relates to hot runnermanifold systems used for injection molding. The invention hasparticular utility in large cavitation systems.

BACKGROUND OF THEE INVENTION

The state of the art includes various arrangements for hot runnermanifold systems to transfer molten material, typically plastic resin,from an injection molding machine to a mold. Hot runner manifold systemsare well known and typically include a manifold plate, a manifold housedin the manifold plate, and a backing plate that supports the manifoldand manifold plate. The manifold system routes molten material from acentral sprue, which connects to an injection unit on an injectionmolding machine, to a plurality of nozzles which inject the moltenmaterial into cavities in the mold. The manifold system divides the flowof the molten material into several branches as it flows from thecentral sprue to the nozzles. It is desirable that flow of moltenmaterial through the manifold system be balanced so that materialarriving at each nozzle has approximately the same temperature andpressure to produce uniform parts in each mold cavity. Toward that end,manifold systems are preferably designed so that each branch providessubstantially the same size and length of flow path for the moltenmaterial. With uniform flow paths at each branch, temperature andpressure differences between branches should be minimized. However, formolds with a high number of cavities, such uniform flow paths are notalways possible due to location limitations on the manifold.

Referring to FIGS. 1 and 2, a prior art manifold system using two platesis shown with portions of the plates and main manifold cut away toreveal internal detail. For injection molding systems with many cavitiesin the mold, a manifold assembly 10 has a plurality of sub-manifolds 12arranged in manifold plate 14 and fed by a main manifold 16 mounted inbacking plate 18. Sprue 20 connects to the main manifold 16 at a centrallocation. Main manifold 16 has a melt channel 22 with branches to eacharm 24 of main manifold 16 and connecting to an inlet of eachsub-manifold 12. Each sub-manifold 12 has its own melt channel networkthat communicates the molten material from main manifold 16 to nozzles(not shown) connected to each sub-manifold 12. In the exampleillustrated, each sub-manifold 12 accommodates twenty-four nozzles.Typically, valve-gate type nozzles are used with such a system, and havepneumatic valve actuators at the upper end of the nozzle that actuatevalve stems in the nozzle. The valve stems extend through apertures 26in the sub-manifolds 12 and the actuators are housed in actuatorcavities 28 formed in backing plate 18.

Such prior art manifold systems have significant limitations andshortcomings. Specifically, since the main manifold 16 and actuatorcavities 28 are both in backing plate 18, and the main manifold 16cannot pass through actuator cavities 28, the transverse spacing ofactuator cavities 28, and hence the nozzles, can be greater thandesired. That leads to the mold being larger than optimum, and flowlength of the molten material being increased.

Air lines 30 are routed to each actuator through the backing plate 18.The location of the air lines is constrained by the location of themanifold 16. Also since the location of the arms 24 of main manifold 16is constrained by the location of actuator cavities 28, flow of moltenmaterial to portions of sub-manifolds 12 is not optimum. In the exampleillustrated, arm 24 a conducts molten material through melt channel 22to branches 32 a and 32 b to two sub-manifolds 12 a and 12 b at portions34 a and 34 b located at the periphery of sub-manifolds 12 a and 12 b.Material then flows to a central location in the sub-manifolds andsubsequently through multiple channels to the nozzles. Such a flow pathincreases the likelihood of the molten material having less uniformtemperature and pressure throughout the sub-manifolds 12, which can leadto unbalance in the system.

Physical coupling, typically through the use of bolts, between thebacking plate 18 and the manifold plate 14 stabilizes the layeredstructure by restricting bowing during the injection cycle. Plate bowingarises as a consequence of the injection pressure and pressure fromspring-loaded seals at interfaces between the sub-manifolds 12 andnozzles and also between the sub-manifolds 12 and the arms 24 of themain manifold 16. If the plates bow, leakage can occur at thoseinterfaces. Pillars 36 are provided in manifold plate 14 where possible,and numerous bolt holes 38 are provided through backing plate 18 tofacilitate such bolting. However, bolts cannot be put through the meltchannel 22 of manifold 16, so to make the bolt spacing adjacent themanifold 16 as tight as possible, the arms 24 of manifold 16 are made asnarrow as possible. To maintain structural integrity of such narrowportions, the manifold 16 may have to be hardened or be made from astronger material than is desirable.

SUMMARY OF THE INVENTION

The present invention provides an manifold system for an injectionmolding system comprising a main manifold with at least one arm, atleast one sub-manifold spaced from the main manifold, and a plurality ofmelt transfer bushings between the main manifold and each sub-manifold.The main manifold has a main melt channel branching to each arm with anoutlet at each branch. Each sub-manifold has an inlet and a plurality ofsecondary melt channels in communication with the inlet. Each melttransfer bushing is disposed between one of the sub-manifolds and one ofthe arms of the main manifold, and provides communication between theoutlet of one of the arms of the main manifold and the inlet of one ofthe sub-manifolds. An air plate is disposed between the main manifoldand the at least one sub-manifold, and between a backing plate, thatpreferably houses the main manifold, and a manifold plate, thatpreferably houses the at least one sub-manifold. The air plate has aplurality of actuator cavities for receiving actuators for nozzles. Theair plate also has a plurality of air channels therein which communicatewith the actuator cavities for conducting fluid, in use, to theactuators. The air plate also preferably has a plurality of coolingchannels for conducting cooling fluid, in use, to cool the air plate.

The air plate preferably has a plurality of air plate bolt holes, whichreceive bolts to secure the air plate to the manifold plate. A pluralityof the air plate bolt holes may be disposed directly beneath the mainmanifold. The backing plate has a plurality of backing plate bolt holeswhich receive bolts to secure the backing plate to air plate. Aplurality of the backing plate bolt holes are disposed directly abovesub-manifolds.

Each melt transfer bushing has a melt channel therein and preferably astatic mixer is disposed in the melt channel to homogenize the moltenmaterial at the entrance to each sub-manifold. Preferably each melttransfer bushing has a heating device, such as an electric heater or atleast one heat pipe which transfers heat from the main manifold and asub-manifold to the melt transfer bushing.

Preferably, a plurality of valve gate nozzles are connected to eachsub-manifold, each nozzle has a melt channel in communication with asecondary melt channel in a sub-manifold, and each nozzle has a valvegate actuator disposed in one of the actuator cavities in the air plate.Each sub-manifold has a plurality of manifold bushings aligning with thenozzles and providing the communication between the melt channel in thenozzles and the secondary melt channels in the sub-manifold. Eachmanifold bushing has a flat sealing surface, and each nozzle preferablyhas a non-flat sealing surface adjacent the flat sealing surface of themanifold bushing, which reduces the force required to adequately sealthe sealing surfaces. Preferably the non-flat sealing surface is araised conical surface around a melt channel of the nozzle angled lessthan one degree from planar.

Similarly, the main manifold preferably has a flat sealing surface, andthe melt transfer bushing preferably has a non flat sealing surfaceadjacent the flat sealing surface.

The invention provides the opportunity for flow paths in such manifoldsto be routed where needed without regard to nozzle location. Theinvention also provides the opportunity for a mixer to be inserted ateach melt transfer bushing between manifolds to thereby enhance mixingof resin being conducted therethrough and balancing of the system.

Thus, the present invention provides an improved manifold and plateassembly, which overcomes the limitations and shortcomings of the priorart.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will not be describedwith reference to the accompanying drawings, in which:

FIG. 1 is an isometric view of a prior art manifold assembly withportions of plates and the manifold shown cut away;

FIG. 2 is a detail view of a portion of FIG. 1;

FIG. 3 is an is isometric view of a preferred embodiment of the presentinvention with portions of plates and the manifold shown cut away;

FIG. 4 is a detail view of a portion of FIG. 3;

FIG. 5 is a section view of a preferred embodiment of the inventionillustrating positional relationships among components;

FIG. 6 is a detail view of a portion of FIG. 5;

FIG. 7 is the view of FIG. 6 illustrating an alternate embodiment for anozzle configuration; and

FIG. 8 is a further detailed view of a portion of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIGS. 3-5, an example of the preferred embodiment of amanifold assembly of the present invention is illustrated and generallyindicated by the reference numeral 50. The hot runner manifold system 50has a plurality of sub-manifolds 52 that are preferably arranged andhoused in manifold plate 54 and are fed by a main manifold 56 preferablyhoused in backing plate 58. As with the prior art manifolds, a sprue 60connects to the main manifold 56 at a central location, and mainmanifold 56 has a main melt channel 62 that branches into arms 64 ofmain manifold 56. Arms 64 may branch in several different directions,such as is illustrated, or a manifold may have only two arms aligned andextending opposite from each other and from sprue 60 to make a linearmanifold. The manifold may also have only one arm, which in that case,functions to offset the flow in one direction only. Each arm has anoutlet 63 of a branch of the main melt channel 62 that is incommunication with the inlet 65 of one of the sub-manifolds 52. Thebacking plate 58 is spaced from the manifold plate 54, so that mainmanifold 56 is spaced from the sub-manifolds 52, and at each arm 64 ofmain manifold 56 a melt transfer bushing 68 connects the outlet 63 ofthe main melt channel 62 to the inlet 65 of a sub-manifold 52. Eachsub-manifold 52 has a plurality of secondary melt channels 104 incommunication with inlet 65 and nozzles 92 connected to sub-manifold 52.Each sub-manifold 52 has apertures 66 through which valve stems forvalve-gated nozzles pass.

Between the manifold plate 54 and the backing plate 58 is an air plate70 that has a plurality of actuator cavities 72 for nozzle actuators 90as well as a plurality of air channels 74 that conduct actuating fluid,such as air, to the actuators 90. The terms air plate and air channelare used only as labels and are not intended to limit the invention tothe use of air. Other gaseous or liquid fluids can be used with the airplate to actuator the actuators 90. The actuator cavities 72 align withthe apertures 66 in sub-manifolds. 52. Because the actuator cavities 72for the actuators 90 and air channels 74 are not in the same plane asthe main manifold 56, the main manifold 56 can take an optimum path tothe sub-manifolds 52. Flow through the sub-manifolds 52 can be betterbalanced by introducing the molten material centrally rather than at oneend of the sub-manifold 52, and the overall spacing of the actuatorcavities 72, and hence the nozzles, can be closer, thereby reducing theoverall size of the manifold and mold compared to the prior art.

Air plate 70 preferably has cooling channels 84 that, in use, conductcooling fluid, such as water, through air plate 70, preferably proximateto actuator cavities 72 so that air plate 70 is sufficiently cool toprevent seal degradation for actuators 90 in actuator cavities 72.Cooling of air plate 70 also enhances thermal isolation between mainmanifold 56 and 15 sub-manifolds 52, which minimizes thermal variationin sub-manifold 52 and improves the material flow balance in the system.Cooling channels 84 are aligned with and communicate with cooling ports86 in air plate 70, which are aligned with and communicate with coolingports 88 in manifold plate 54 and cooling ports 116 in backing plate 58.

Cooling ports 116 may be arranged to align with and communicate withcooling ports 118 in a platen 119 of an injection molding machine inwhich manifold system 50 can be installed. Preferably o-rings 121, orsimilar types of seals, are used to provide sealing between adjacentplate faces at interfaces of cooling ports 86, 88 and 116. Sucharrangement of cooling lines and ports in the plates 54, 58, and 70eliminate the need for any cooling fluid hoses to be attached directlyto the manifold system 50. Cooling fluid is received directly from theplaten, to which cooling fluid hoses are attached. This reduces the timenecessary to remove manifold system 50 from the injection moldingmachine since there are no hoses or hose fittings to disconnect from themanifold system 50.

Bolting together of the plates 54, 58 and 70 is also improved with thepresent invention. Air plate 70 can be bolted to manifold plate 54 asdesired with little concern for location of main manifold 56 since bolts76 extend only between the air plate 70 and manifold plate 54. Aplurality of air plate bolt holes 78 in air plate 70 provide for suchbolting, with air plate bolt holes 78 running under main manifold 56 asneeded to best counteract forces tending to separate the plates. Thebacking plate 58 can then be bolted to air plate 70 with little concernfor the position of sub-manifolds 52, since bolts 80 extend only betweenbacking plate 58 and air plate 70. Backing plate bolt holes 82 can belocated very close to where separation forces occur near ends ofmanifold arms 64, and directly over a sub-manifold 52. The better platebolting of the present invention provides less likelihood of platebowing, and thereby less likelihood of resin linkage at interfacesbetween components.

In the embodiment illustrated in FIG. 5, air plate 70 is shown as arelatively thin plate while manifold plate 54 and backing plate 58 bothare thicker with pockets that house the sub-manifolds 52 and mainmanifold 56 respectively. Alternatively, the air plate 70 could bethicker and incorporate the pockets to house the main manifold 56 and/orthe sub-manifolds. Such an arrangement allows manifold plate 54 and/orbacking plate 58 to be substantially thinner plates, either bolting toair plate 70.

Referring to FIGS. 5 and 6, sub-manifolds 52 are constructed andarranged such that a plurality of nozzles 92 connect to them in a mannerwell-known in the art. Any nozzle configuration and any nozzleattachment method known in the art can be used with sub-manifold 52. Forexample, in the embodiment illustrated, nozzle 92 is spring-loadedagainst a manifold bushing 94 by spring 96. Nozzle 92 preferably has anon-flat sealing surface 98 adjacent the flat sealing surface 100 ofmanifold bushing 94, which reduces the force required to adequately sealthe sealing surfaces because of reduced contact area. Preferably thenon-flat sealing surface 98 is a raised conical surface around meltchannel 108 in nozzle 92 that is angled less than one degree from planaras described in U.S. patent application Ser. No. 09/575,353, herebyincorporated herein by reference. A similar sealing interface ispreferably provided between end 102 of melt transfer bushing 68 and mainmanifold 56.

In the embodiment illustrated, manifold bushing 94 communicates with amelt channel 104 in sub-manifold 52 and directs molten material tonozzle 92 through a manifold bushing melt-channel 106 that is alignedwith the axial melt channel 108 in nozzle 92. A sealing interface 112occurs between valve stem 110 and manifold bushing valve stem guidechannel 123 to prevent resin linkage along valve stem 110 to actuator90.

Another example of a nozzle/manifold assembly is illustrated in FIG. 7,where nozzle 120 has a melt channel 122 with a non-axial portion 124that engages a manifold bushing 126 which communicates with melt channel104. A sealing interface 114 occurs between valve stem 128 and a valvestem guide channel 125 in nozzle 120 to prevent resin linkage alongvalve stem 128 to actuator 90.

FIGS. 6 and 7 also illustrate different embodiments for actuator 90. Inthe embodiment illustrated in FIG. 6, actuator 90 is housed in aseparate cylinder 130, which is installed in actuator cavity 72 formedin the bottom of air plate 70. Cylinder 130 seals between the base 132of actuator cavity 72 and a backup pad 134 disposed between sub-manifold52 and air plate 70. Such sealing of a cylinder in an actuator cavitywith a backup pad is described in U.S. Pat. No. 6,343,925 assigned tothe same assignee as the present invention and hereby incorporatedherein by reference. In the embodiment illustrated in FIG. 7, actuatorcavity 72 is formed in the top of air plate 70 and is itself thecylinder for actuator 90. A separate seal plate 136 is optionallyprovided to seal actuator cavity 72, or backing plate 58 itself couldseal actuator cavity 72. This requires each actuator cavity to be acylinder of sufficient quality to allow proper operation of actuator 90,but it does not require any seal that is dependent on the loadsgenerated by installation of components below the air plate 70.

Referring to FIG. 8, another advantage of the hot runner manifold system50 of the present invention is that since the main manifold 56 is spacedfrom the sub-manifolds 52, the melt transfer bushings 68 aresufficiently long to allow installation of a static mixer 140 in theflow channel 148 of each melt transfer bushing. The static mixer 140homogenizes the molten material at the entrance to each sub-manifold 52,thereby providing a more balanced flow of the molten material. Staticmixers suitable for such application are well known. The invention isnot limited to the use of any particular static mixer. An example of onesuitable mixer, as illustrated, is described in U.S. Pat. No. 6,382,528assigned to the same assignee as the present invention and herebyincorporated herein by reference. Mixer 140 has a spiral groove 142around a central shaft 144 with an increasing space between the shaft144 and the lands 146 adjacent the groove 142. Flow of the moltenmaterial through the mixer 140 is transitioned from spiral flow to axialflow and homogenized in the process. Another example of a static mixersuitable for use in melt transfer bushing 68 is a stack of static mixingelements as described in U.S. Pat. No. 6,394,644, herein incorporated byreference.

Melt transfer bushing 68 preferably has a heating device 150 so thatthere is little temperature loss in the molten material as it flowsthrough melt transfer bushing 68. The heating device 150 preferably isan electric heater, but heating device 150 may be at least one heat pipethat draws heat from main manifold 56 and sub-manifold 52 tosufficiently heat melt transfer bushing 68. Alternatively, melt transferbushing 68 could be constructed of a material sufficiently thermallyconductive to not require any heating device 150. Melt transfer bushing68 may itself function as a heat pipe drawing sufficient heat from mainmanifold 56 and sub-manifold 52. Melt transfer bushing 68 is preferablyfastened to sub-manifold 52, such as by bolts 152 (only one of which isshown for clarity) which provide sufficient compressive force betweenthe melt transfer bushing 68 and sub-manifold 52 to seal the interface154 between melt channel 148 in melt transfer bushing 68 and meltchannel 104 in sub-manifold 52. To seal the interface 156 between meltchannel 148 in melt transfer bushing 68 and melt channel 62 in mainmanifold 56, force is exerted by a spring device 158 acting between mainmanifold 56 and backing plate 58 and preferably aligned with meltchannel 148. The main manifold 56 preferably has a flat sealing surface160, and the melt transfer bushing 68 preferably has a non-flat sealingsurface 162 adjacent the flat sealing surface 160. Preferably thenon-flat sealing surface 162 is a raised conical surface around the meltchannel 148 of the melt transfer bushing 68, and is angled less than onedegree from planar, as previously described. Of course, sealing betweenthe melt transfer bushing 68 and main manifold 56 could be achievedusing alternative techniques readily appreciated by one skilled in theart.

With melt transfer bushing 68 fixed to sub-manifold 52 by bolts 152,relative lateral motion between sub-manifold 52 and main manifold 56 dueto thermal expansion differences occurs at interface 156. Because of thehigh frictional load at interface 156 from spring device 158, ratherthan melt transfer bushing 68 sliding relative to main manifold 56 atinterface 156, melt transfer bushing 68 may bend during such movementallowing interface 156 to leak. A centering feature 159, such as a ring,acts between melt transfer bushing 68 and air plate 70 to facilitatesliding of melt transfer bushing 68 relative to main manifold 56 atinterface 156 when there is relative lateral motion between sub-manifold52 and main manifold 56. Centering feature 159 keeps melt transferbushing properly located in air plate 70 and minimizes risk of leakingat interface 156 by minimizing likelihood of melt transfer bushingbending. Alternatively, melt transfer bushing could be madesubstantially stiff to sufficiently resist bending on its own, but sucha design would be more massive, requiring more heat.

The present invention advantageously provides an improved hot runnermanifold system with less likelihood of plate bowing and its associatedleakage, better thermal and geometric balance, and closer nozzle spacingall due primarily to the main manifold being spaced from thesub-manifolds. The additional space also allows for insertion of an airplate that provides all the air for valve gate actuators as well ascooling fluid to better thermally isolate the main manifold from thesub-manifolds and to simplify installation and removal of the manifoldsystem from an injection molding machine. There is also room for staticmixers in melt transfer bushings between the main manifold andsub-manifolds to improve melt homogeneity. The invention provides theopportunity for flow paths in such manifolds to be routed where neededwithout regard to nozzle location. The invention also provides theopportunity for a mixer to be inserted at each melt transfer bushingbetween manifolds to thereby enhance mixing of resin being conductedtherethrough and balancing of the system.

It will, of course, be understood that the above description has beengiven by way of example only and that modifications in detail may bemade within the scope of the present invention. For example, it will beappreciated by one skilled in the art that more than two levels ofmanifolds may be supported by the invention. Sub-manifolds 52 may begrouped, for example, in groups of four, with each group fed by an “X”shaped manifold. Two, four, or more of those X-shaped manifolds withtheir sub-manifolds may be grouped and fed by another manifold. Suchlayering of manifolds can continue for as much space as the platenspacing of the molding machine allows.

It will also be appreciated by one skilled in the art that a manifoldsystem of the present invention can be used with hot-tip type nozzlesinstead of valve gate type nozzles. With no valve gate to actuate, theair plate has no actuator cavities and no air channels, but can havecooling channels. The benefits of separating the main manifold from thesub-manifolds when used with hot-tip type nozzles are improved thermalisolation between the main manifold and sub-manifolds, which can beenhanced by cooling the air plate, and the ability to install staticmixers in the melt transfer bushings to homogenize the melt and betterbalance the system.

1. A manifold system for an injection molding system, the manifoldsystem comprising: a main manifold (56) having a plurality of arms (64)and a main melt channel (62) therein branching to each arm (64), with anoutlet (63) at each arm (64); at least one sub-manifold (52) spaced fromthe main manifold (56), each sub-manifold (52) having an inlet (65) anda plurality of secondary melt channels (104) in communication with theinlet (65); a plurality of melt transfer bushings (68), each melttransfer bushing (68) disposed between one sub-manifold (52) and one arm(64) of the main manifold (56), each melt transfer bushing (68)providing communication between the inlet (65) of said one sub-manifold(52) and the outlet (63) of said one arm (64); a backing plate (58); amanifold plate (54) spaced form the backing plate (58); an air plate(70) disposed between the backing plate (58) and the manifold plate (54)and disposed between the main manifold (56) and the at least onesub-manifold, the air plate (70) having a plurality of actuator cavities(72) for receiving actuators (90), the air plate (70) having s aplurality of air channels (74) communicating with the actuator cavities(72) for conducting fluid, in use, to actuators (90).
 2. The manifoldsystem of claim 1, wherein the main manifold (56) is housed in thebacking plate (58).
 3. The manifold system of claims 1 or 2, wherein theat least one sub-manifold (52) is housed in the Manifold plate (54) 4.The manifold system of any of the preceding claims, wherein the airplate (70) has a plurality of cooling channels (84) for conductingfluid, in use, to cool the air plate (70).
 5. The manifold system ofclaim 4, wherein the cooling channels (84) are proximate the actuatorcavities (72).
 6. The manifold system of any of the preceding claims,wherein the air plate (70) has a plurality of air plate bolt holes (78)which receive bolts (76) to secure the air plate (70) to the manifoldplate (54).
 7. The manifold system of claim 6, wherein some of the airplate bolt holes (78) are disposed directly beneath the main manifold(56).
 8. The manifold system of any of the preceding claims, wherein thebacking plate (58) has a plurality of backing plate bolt holes (82)which receive bolts (80) to secure the backing plate (58) to the airplate (70).
 9. The manifold system of claim 8, wherein some of thebacking plate bolt boles (82) are disposed directly above a sub-manifold(52).
 10. The manifold system of any of the preceding claims, furthercomprising a plurality of valve gate nozzles (92, 120) connected to eachsub-manifold (52), each nozzle (92, 120) having a melt channel (108,122, 124) in communication with a secondary melt channel (104) in asub-manifold (52), each nozzle (92,120) having an actuator (90) disposedin one of the actuator cavities (72).
 11. The manifold system of claim 9or 10, wherein each sub-manifold has a plurality of manifold bushings(94, 126), each manifold bushing (94, 126) being aligned with one of thenozzles (92, 120) and providing the communication between the meltchannel (108, 122, 124) in the nozzle (92, 120) and the secondary meltchannel (104) in the sub-manifold (52).
 12. The manifold system of claim11, wherein each manifold bushing (94) receives a valve stem (110)extending from one of the actuators (90), through the manifold bushing(94), and through the nozzle (92), the valve stem (110), in use, beingmoved by the actuator (90) to start and stop the flow of molten materialthrough the nozzle (92).
 13. The manifold system of claim 11 or 12,wherein each manifold bushing (94) has a flat sealing surface (100), andwherein each nozzle (92) has a-non-flat sealing surface (98) adjacentthe flat sealing surface (100) of the manifold bushing (94).
 14. Themanifold system of claim 13, wherein the non-flat sealing surface (98)is a raised conical surface around a melt channel (108) of the nozzle(92) angled less than one degree from planar.
 15. The manifold system ofany of the preceding claims, wherein the main manifold (56) has a flatsealing surface (160), and wherein the melt transfer bushing (68) has anon-flat sealing surface (162) adjacent the flat sealing surface. 16.The manifold system of claim 15, wherein the non-flat sealing surface(162) is a raised conical surface around the melt channel (148) of themelt transfer bushing (68) angled less than one degree from planar. 17.The manifold system of any of the preceding claims, wherein each melttransfer bushing (68) has a melt channel (148) therein and furthercomprising a static mixer (140) disposed in the melt channel (148). 18.The manifold system of any of the preceding claims, wherein each melttransfer bushing (68) has a heating device (150).
 19. The manifoldsystem of claim 18, wherein the heating device (150) is one of: anelectric heater; and at least one heat pipe arranged to transfer heatfrom the main manifold (56) and a sub-manifold (52) to the melt transferbushing (68).
 20. The manifold system of any of the preceding claims,further comprising: at least one centering feature (159), each centeringfeature (159) being associated with a melt transfer bushing (68) andacting between the air plate (70) and the melt transfer bushing (70) tofacilitate sliding of melt transfer bushing (68) relative to mainmanifold (56) at their interface (156) when there is relative lateralmotion between sub-manifold (52) and main manifold (56).
 21. A manifoldsystem for an injection molding system, the manifold system comprising:a main manifold (56) having a main melt channel (62) therein with anoutlet (63); a sub-manifold (52) spaced from the main manifold (56), thesub-manifold (52) having an inlet (65) and a plurality of secondary meltchannels (104) in communication with the inlet (65); a melt transferbushing (68), disposed between the sub-manifold (52) and the mainmanifold (56), the melt transfer bushing (68) providing communicationbetween the inlet (65) of the sub-manifold (52) and the outlet (63) ofthe main manifold (56); a backing plate (58); a manifold plate (54)spaced form the backing plate (58); an air plate (70) disposed betweenthe backing plate (58) and the manifold plate (54) and disposed betweenthe main manifold (56) and the sub-manifold, the air plate (70) having aplurality of actuator cavities (72) for receiving actuators (90), theair plate (70) having s a plurality of air channels (74) communicatingwith the actuator cavities (72) for conducting fluid, in use, toactuators (90).